Clean rooms fall into different classes, based on the size of the allowable contaminant. For example; if memory serves a class 10 clean room would only allow contaminants that are less than 0.1 micron in spherical size. Then a class 100 would only allow particles that are less than 0.01 microns. It would also depend on the weather you are trying filet out dust contaminants or biological contaminants also. Usually for biological contaminants you always use a minimum of 0.25" WG and a Heppa filtration type system. As far as the air handler goes you will need a handler that can handle the back pressure of the filtration system, you actually need a unit that is designed for it so that you do not waste energy with excessive back pressure. Also, the room must have a pressurized airlock that will not allow contaminants to flow into the clean room. You would be best served by a Liebert type system, that maintains total environmental quality. Especially if you are making a precision piece of electronic equipment. ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################